يحافظ المرشد على التنوع الأحيائي.

يحافظ is a present-tense / imperfect verb meaning he preserves, he maintains, or he protects depending on context.

It comes from the root ح ف ظ, which is connected with ideas like preserving, guarding, and keeping.

More specifically, it is from Form III:

• past: حافَظَ
• present: يُحافِظُ

So in this sentence, يحافظ means he preserves / maintains.

Because in Arabic, the verb حافظ / يحافظ is commonly used with the preposition على.

So:

• حافظ على الشيء
• يحافظ على الشيء

means:

• to preserve something
• to maintain something
• to protect something

This is something you largely have to learn as a fixed pattern:

• يحافظ على البيئة = he protects the environment
• يحافظ على صحته = he maintains his health
• يحافظ على التنوع الأحيائي = he preserves biodiversity

So the preposition is not optional here; it is part of how the verb is normally used.

Because verb-first word order is very common in Modern Standard Arabic.

This sentence is:

• يحافظ = preserves
• المرشد = the guide
• على التنوع الأحيائي = biodiversity / biological diversity

So the structure is:

• Verb + Subject + Prepositional phrase

This is completely normal in Arabic.

You could also say:

• المرشد يحافظ على التنوع الأحيائي

That is also correct, but it gives a slightly different emphasis, more like The guide preserves biodiversity with extra focus on the guide.

المرشد means the guide or the instructor/adviser, depending on context.

It is:

• masculine
• singular
• definite because it has الـ

In this sentence, it is the subject of the verb يحافظ.

If full case endings were written, it would be:

• المرشدُ

because the subject is in the nominative case.

The الـ makes it definite, so المرشد means the guide, not just a guide.

Arabic often uses definiteness more explicitly than English. Here, the sentence refers to a specific guide, or to the guide as a known role.

Compare:

• مرشد = a guide
• المرشد = the guide

It is best understood as a noun + adjective phrase, not an idaafa.

• التنوع = the diversity
• الأحيائي = biological

Together:

• التنوع الأحيائي = biological diversity

Why is it not an idaafa?

Because in an idaafa, the second word usually does not take الـ if it is simply the second noun in the construction. But here الأحيائي does take الـ, and it functions as an adjective describing التنوع.

So this is a regular noun-adjective combination.

Because adjectives in Arabic usually match the noun they describe in:

• definiteness
• gender
• number
• case

Since التنوع is definite, the adjective must also be definite:

• التنوع الأحيائي = the biological diversity

If the noun were indefinite, the adjective would also be indefinite:

• تنوع أحيائي = biological diversity / a biological diversity

So both words have الـ because the noun is definite and the adjective agrees with it.

Yes. The preposition على makes the following noun genitive.

So in fully vowelled Arabic, you would have:

• على التنوّعِ الأحيائيِّ

The written sentence without case endings looks like:

• على التنوع الأحيائي

But grammatically:

• التنوعِ is genitive because it follows على
• الأحيائيِّ is also genitive because it is the adjective modifying التنوع

This is a very common pattern in Arabic: preposition + genitive noun, with any following adjective matching it.

It is pronounced approximately:

• al-aḥyāʾī

A rough breakdown:

• ال = al-
• أحيا has the ḥ sound, a strong breathy h
• there is a hamza in the middle: āʾ
• it ends with a long ī

So the word may feel a bit difficult at first because of the sequence of vowels and the hamza.

It comes from أحياء relating to living things / life sciences, and أحيائي means biological.

Yes, التنوع الأحيائي is a standard Modern Standard Arabic term for biodiversity.

You may also encounter:

• التنوع البيولوجي

This is another common equivalent, using a more international/loan-based adjective.

So both can be found, but التنوع الأحيائي is a very natural MSA expression.

In this sentence, the subject is singular, so the singular verb is expected:

• يحافظ المرشد

But your question points to an important Arabic rule:

When the verb comes before the subject in MSA, the verb often stays singular, even if the subject is plural.

For example:

• يحافظ المرشدون على التنوع الأحيائي
  = The guides preserve biodiversity.

Here, with verb-first order, many grammar traditions treat the verb as singular masculine يحافظ even though المرشدون is plural.

But if the subject comes first, full agreement is used:

• المرشدون يحافظون على التنوع الأحيائي

That is a very useful pattern to know in MSA.

المرشد comes from the root ر ش د, which has to do with:

• guidance
• right direction
• sound judgment

Related words include:

• رَشَد = right guidance / maturity
• إرشاد = guidance
• مُرشِد = guide

So المرشد literally means the one who guides.

Yes. Depending on context, يحافظ على can be translated in several close ways, including:

• preserves
• maintains
• protects
• conserves

So if the context is environmental or ecological, conserves biodiversity is a very natural translation.

That is one reason Arabic learners should pay attention not only to the dictionary meaning of يحافظ على, but also to the context in which it is used.